You should also try to have most courses in the same direction. Or atleast make sure that people aren't facing each other on a narrow track on a hillside. One going up and the other on the way down...
Also, try to do some calculations on the different route choices of a leg. On a tricky singletrack you might be doing 15km/h (10miles/h) and on a dirt road or a nice smooth track you're going three times as fast.
IOF has some maps from the world cup on thier homepage that will give you some ideas of the MTBO specifications and course planning:
http://orienteering.org/mtb-orienteering/maps/